Video transmission of MPEG-2 is performed at a fixed rate in TS format. When TS packets are transmitted over an IP network, transmission delay fluctuation occurs in the network. For normal video transmission, it is required to transmit TS packets to a decoder with the time interval generated by an encoder being maintained. However, occurrence of the transmission delay fluctuation may result in failed decoding because intervals of TS packet arrival to the decoder become irregular, which may lead to disorder of audio video (AV) or AV synchronization error. Patent Literature 1 is a technical document as to absorbing the transmission delay fluctuation. Patent Literature 1 discloses a method of providing a buffer to absorb transmission delay fluctuation, monitoring the amount of buffer accumulation at a certain timing (sample time), and setting the output rate according to the accumulated amount.